This invention relates to the structure of a head house region of a magnetic tape cassette.
A magnetic tape cassette has in its front part a head house region, so called because it admits the head, along with capstans, pinch rollers, and other elements for driving the tape, of a recording-playback apparatus into the cassette space where the tape runs. The head house region usually includes a plurality of tape guide groups arranged symmetrically with respect to the centerline of the magnetic tape cassette and formed integrally with the half housing sections of the cassette to ensure stable running of the tape. With improvements in performance of magnetic tape cassettes in recent years, vibrations that result from the frictional contact between the tape guides and the tape and are thence transmitted to the tape, have attracted growing attention as a cause of increased modulation noise. In an effort to solve this problem and thereby reduce the modulation noise and achieve phase stabilization, it has already been proposed, as shown in FIG. 5, to form all of the plurality of tape guides 1a-1f in an independent one-piece guide block 1. The guide block 1 of the construction does accomplish both the reduction of modulation noise and the phase stabilization at which the present invention is aimed. However, as is clear from FIG. 5, the construction eliminates integral ribbing from the lower half housing section 3 and also from the upper half housing section (of a similar construction not shown) over a fairly large percentage of the longitudinal dimension of the magnetic tape cassette. This results in inadequate strength of the lower and upper half housing sections against warping during fabrication, adversely affecting the parallelism of the two half housing sections. It might appear possible to remedy the shortcoming by increasing the thickness of the base plate of the head house region up to the space (tape-accommodating space) inside the half housing section until sufficient rigidity is secured. In fact, it would necessitate a base plate as thick as 3.5 mm. Such a thick plate would cause sink, not only presenting appearance and dimensional problems but also extending the cooling time after injection molding, with consequent increases in both overall time period of molding cycle and production cost.